Electromagnetic device



Dec. 4, 1934. w. M. HILL ELECTROMAGNETIC DEVICE Filed July 7, 1950 2 Sheets-Sheet l v I 4 g 1 i I P I; 2

.A TTURNEY DEC. 4, 1934. w M H 1,982,811

ELECTROMAGNETIC DEVICE Filgd July 7 1930 2 Sheets-Sheet 2 A TTO/P/VEY PATENT oFFics UNITED STATES 1,982,811 ELECTROMAGNETIC DEVICE Walter M. Hill, Baltimore, Md., assignor to West ern Electric Company, Incorporated, New York, N. Y., a corporation of New York Application July 7, 1930, Serial No. 466,068

Claims.

This invention relates to electromagnetic devices, and more particularly to electromagnetic relays and the like.

An object of the invention is to provide a sim- 5 pie and inexpensive electromagnetic device which is extremely sensitive, quick acting, and efllcient 'in its operation.

In accordance with the above object, one embodiment of the invention contemplates the provision of an electromagnetic relay, wherein an armature pivoted between spaced laminated pole pieces is statically and dynamically balanced so that a small magnetic flux passing across the air gaps between the pole pieces s suillcient to rotate the armature to closethe relay contacts. The armature is returned to its normal position by means of a spring which is connected therewith through an eccentric arm so that the torque produced by the spring is sub- 2o stantially constant throughout the range of movement of the armature. The armature and contacts of the relay are so constructed and interconnected that when the contacts are closed they are undisturbed by slight movements of the armature due to mechanical vibration or other extraneous causes. A more complete understanding of the invention will be had from the following detailed description when read in conjunction with the so accompanying drawings, wherein Fig. 1 is an isometric projection of an electromagnetic relay embodying the features' of the invention;

Figs. 2 and 3 are front and side elevational views thereof, partly in section, with the relay contacts shown closed;

Fig. 4 is a fragmentary detailed section on line 4-4 of.Fig. 2; and

Pig. 5 illustrates, diagrammatically, an elec- 'trical testing system employing an electromagnetic relay embodying the present invention.

Although the invention is herein illustrated and described in connection with an alternating current relay, it should be understood that the novel features of the invention may be employed advantageously in various other types of electromagnetic devices operated either by alternating or direct current.

Referring now to the drawings wherein like reference numerals designate like parts throughout the several views, it will be observed that an alternating current relay embodying the features of the present invention is indicated generally by the numeral 10 and comprises a lami- 55 nated core 12 in the form of an open rectangular loop having a vertical portion 13 extending axially through a magnetizing coil 14 and termimating in end portions or pole pieces 16 and 17 which are horizontally and vertically spaced from each other to provide a plurality of air gaps therebetween. The pole pieces 16 and 17 are each provided with the usual shading coil 18.

The core 12 comprises a plurality of laminations of magnetic material, preferably silicon steel, the laminations being insulated from each other in any well known manner and rigidly clamped together between spaced angle supports 19, 19 and spaced front and rear plates 20 and 21, respectively. A statically and dynamically balanced armature 23 is pivoted intermediate its ends between the front and rear plates 20 and 21, and is adapted to be rotated against the action of a coil spring 22 to bridge the air gapsbetween the upper and lower pole pieces 17 and 16 when a magnetic flux passes across the air 75 gap. The armature 23 comprises spaced halves 24 and 25 (Fig. 4), each half consisting of a plurality of laminations of magnetic material, preferably silicon steel, the laminations being secured to a shaft 26 rotatably supported between adjustable pivot screws 2'727 threaded in the front and rear supporting plates.

The spring 22 which returns the armature to its normal position is attached at one end to a right angle. bracket 28 adjustably secured to the rear supporting plate 21. The opposite end of the spring is attached to one end of an eccentric arm 30 which is secured intermediate its ends to the armature shaft 26 between the armature halves 24 and 25. It will be noted that the arm 30 is angularly disposed with respect to the armature and is rotatable with the armature. The angular relationship is such that the torque produced by the eccentric arm 30 and the spring 22 remains substantially constant throughout the movement of thearmature. An adjustable thumb screw 32 threaded in a laterally projecting portion 33 of the rear supporting plate serves as a stop for limiting the movement of the arma ture under the action of the spring.

The rear supporting plate 21 is formed wit spaced vertical portions which extend upwardly above the armature 23 and terminate in horizontal portions 37 and 38, respectively. A contact blade 40 is secured to the horizontal portion 37 and a resilient contact spring 41 is attached at one end to the horizontal portion 38. The contact blade 40 and contact spring 41 are preferabLv composed of nickel silver and are insulated from the supporting plate by fibre washers 43, 43. Carried upon the free end of the contact spring 41 and on the under side thereof is a tungsten contact point 44 which is adapted to engage a similar contact point 42 attached to the upper side of the contact blade 40.

The contact spring 41,is operatively connected to the armature 23 through a push rod 45 which comprises a body portion 46 of hard rubber or other suitable non-conducting material having a pin 47 partially embedded in the wedge shaped lowerportion thereof and a rigid wire hook 48 partially embedded in the upper portion thereof, the pin and hook being disposed in spaced end to end relation (Fig. 2)

and thereby insulated from each other. The push rod is pivotally suspended from the contact spring 41 by means of the wire hook 48 which is loosely connected to spaced downwardly projecting tongue portions 4949 of the contact springs. The pin 47 is adapted to'slide freely between the-spaced half portions 24 and 25 of the armature through an apertured horizontal plate 50 which rests upon and bridges the spaced halves of the armature. The plate is formed with a vertical portion 51 by means of which it is secured to the armature shaft 26 so as to be rotated with the'armature.

It is believed that the operation of the improved relay will be clearly understood from the above description. The spring 22 normally holds the armature 23 disengaged from the pole pieces 16 and 17 as shown in Fig. 1. With the armature in this position, the relay contact 44 is held spaced from the relay contact 42 through the push rod 45 interposed between the armature and the contact spring 41. When an alternating electrical current is passed through the relay winding 14, an alternating magnetic flux passes across the air gaps between the pole pieces 16 and 17 and causesthe rotation of the armature toward the pole pieces to the position shown in Fig. 2. This movement of the armature releases the upward pressure on the contact spring 41 through'the push rod 45, whereupon. the contact 44 is pressed downwardly into engagement with the contact 42 under the tension of the contact spring 41 and the weight of the" push rod 45. When the relay contacts are closed, the body portion 46 of the push rod. is slightly spaced from the armature plate 50 as clearly shown in Fig. 2, and therefore the relay contacts are not disturbed by slight movements of the armature due to mechanical vibration or other extraneous causes.

The statically and dynamically balanced construction and arrangement of the armature 23 and the arrangement of the relay contacts with respect to the armature contribute to provide a relay which may be readily adjusted to operate quickly and efilciently on an extremely small amount of current, and which is undisturbed by external conditions.

The electromagnetic device, of the present invention may be employed to particular advantage in conjunction with a system for testing insulation on electrical conductors. Such a system is illustrated diagrammatically in Fig. 5

and may consist of a rotatable spool or reel 60 I containinga supply of insulated wire 61 having its inner end bared and electrically connected to the reel, the latter being grounded through itsvsupport 62. The outer end of the wire is similarly connected to a driven take-up reel 64, which is grounded through its support 65. As the wire is drawn from the supply reel and wound upon the take-up reel, it passes through a metal tube 67 which is connected to one end of a secondary winding 68 of a high potential transformer 69, the other end of the secondary winding being grounded. A primary winding 70 of the transformer is connected in serieswith a noninductive resistance 71 across the mains 72 and 73 of a suitable source of alternating electrical energy. Connected across the mains 72 and 73 in parallel with the primary winding 70 and the resistance 71 is an inductive resistance 74 in series with a noninductive resistance 75. The inductive resistance 74 has the same value of impedance as the primary winding 70 of the transformer and the noninductive resistance 75 is equal in value to the resistance 71.

resistance 74, and non-inductive resistances 71 and 75, constitute the four branches of a bridge circuit 80, which is balanced as long as there is no current passing in the secondary winding 68 of the transformer.

The magnetizing coil 14 of the electromagnetic relay of the present invention is connected across the bridge in the manner shown in Fig. 5. The contacts 40 and 41 of the relay are connected across the mains 72 and 73 in series with a signal lamp 82, an interlocking relay 83, and a normally'closed reset switch 84. The interlocking relay is arranged so as to main- Thus it will be understood that .the primary transformer winding 70, inductive tain the lamp circuit closed until the reset switch 84 is opened.

In operating the above described testing system, the inner end of an insulated wire such as rubber covered wire is electrically connected to the grounded supply reel 60 and the outer end thereof is passed through the metal tube 67 and connected to the grounded take-up reel 64. With the transformer 69 connected to the source of alternating electrical energy, the reset switch 84 is closed and the take-up reel is rotated to draw the insulated wire from the supply reel through the metal tube 67. As long as the insulation on the wire traveling through the metal tube is satisfactory, the secondary circuit of the transformer will not be completed from the tube through the wire and. the reels to ground, and therefore the bridge circuit 80 will remain balanced and no operatingcurrent will flow throughthe magnetizing coil 14 of the relay 10. However, when a defective portion of insulation passes through the-metal tube 67, the dielectric strength thereof is not suflicient to withstand a high potential and an electric current will bridge the gap between the metal tube and the wire, thereby completing the secondary circuit of the transformer. through ground. This breakdown of the insulation results in a variation of current through the primary winding 70 of the transformer, thereby disturbing the balance of the bridge 80 which results in a flow of current through the magnetizing coil 14 of the relay 10. This results in the magnetization of the relay core which causes cated and noted the imperfection after which the switch 84 is opened to de-energize the interlocking relay'and open the lamp circuit. The switch 84 is then closed to reset the system for resuming the testing operation.

It is to be understood that the invention is not limited to the particular embodiment thereof herein illustrated and described, except in so far as is defined by the appended claims.

What is claimed is:

1. In an electromagnetic device, a magnetizable core having spaced pole portions, an armature pivoted intermediate its ends between the pole portions of the core and movable thereby, a contact element controlled by the armature and a control element pivoted to the contact eleqnent and loosely connected to the armature in such manner that the armature is undisturbed by movements of the armature .due to extraneous causes.

2. In an electromagnetic relay, an armature pivoted intermediate its ends, a core having spaced pole portions arranged on opposite sides of the armature and adapted to attract opposite ends of the armature to rotate the armature, a pair of contact elements controlled by the armature, means effective upon the rotation of the armature through its attraction by the pole portions of the core for closing the contact elements, a spring for returning the armature to its normal position, and means responsive to the movement of the armature under the action of the spring for opening the contact elements, said last mentioned means being pivoted to said firstmentioned means and in sliding contact with said armature so that it is ineffective upon a 4. In an electromagnetic device, a magnetizable core, an armature, a stationary contact member, a spring-pressed movable contact member, and a means pivotally contacting with said movable contact member and slidingly connected to said armature permitting slight movements thereof without breaking said contacts and adapted to move said movable contact member from contact with said stationary contact member upon extended movements of said armature.

5. In an electromagnetic device, a magnetizable core, an armature, a stationary contact member, a leaf spring, a movable contact member secured to said leaf spring, a push rod pivoted to said leaf spring at one end thereof and slidingly connected to said armature at its opposite end, an enlargement on said push rod adjacent said armature permitting slight movements of said armature without disturbing the contact members and adapted to contact 'with said armature upon extended movements thereof to break the contact between said contact members.

WALTER M. HILL. 

